jordankeck

Ok tuner/datalog pro's, it has been a while since I posted a datalog because I was working on the car, but I now have a number of things replaced and was hoping someone would look at my datalog and see if anything is off. The car has always had in the four years I have owned it hesitation/bogs down. Once the engine is warm, if you shut the car off for 1/2 hour to an hour and restart it, it will run like a champ. I also had good luck in the datalog you see linked below where the car ran pretty good after it had been ran, shut down, and then ran again for a while.

Let me recap what has been changed on the car. Before I purchased the car, and new MSD vented Opti was installed. I replaced the ICM, coil, plugs and wires. I found that my IAC had a broken connector (which turned out to not be a problem), so I replaced the IAC and also scrubbed the throttle body. This made a difference in the response of the car but made no difference to the hesitation/bog. I also replaced the TPS and Intake temp sensor. Since the car is a 93, I just switched over to 4-wire heated O2 sensors this weekend, and pulled the datalog that you see below. The O2's were not new (I picked them up primarily for the connectors to build my own power harness), so I am well aware that those are suspect. Can anyone give me their feedback??

https://drive.google.com/file/d/0B7x...it?usp=sharing

Thanks!
Jordan

jordankeck

I pulled another datalog today while the car was running rough at idle. My IAC counts are very low at 6-8, and I have a pretty good BLM split through the short log file. The car honestly idles like it has a pretty healthy cam - but the entire motor is completely stock with around 130k miles on it.

https://drive.google.com/file/d/0B7x...it?usp=sharing

Can anyone please help??

Jordan

jordankeck

So with all of the knowledge and experience diagnosing issues on this forum, no one has any feedback on why I have split BLM's and low IAC counts at idle? I had hoped that someone would chime in and offer a thought or two about what's causing these issues. I guess I will get out the propane torch and check for vacuum leaks, then check for exhaust leaks. Hopefully I can figure something out...

Injuneer

I usually review these things during a break at work. When you post a .uni file, we need to have a copy of Datamaster to open it, and they no longer allow personal software on my work PC = no Datamaster. So I'm limited to reviewing these at home, and I've had a lot of obligations, and a few files in front of yours. If you could post a .csv file, I could look at it a lot sooner.

Patience is a virtue.

jordankeck

Injuneer, I first want to say that my comments were in no way directed at you. I appreciate every bit of help that you have given me, and your willingness to share your wealth of knowledge is phenomenal! I did not realize that a CSV file is easier, so I exported the 2nd log that I posted to CSV. If you would like to see any other files I will be glad to do the export! Is there any data that I did not export that you would like to see?

https://drive.google.com/file/d/0B7x...it?usp=sharing

Thanks!
Jordan

Injuneer

Got it. I'll take a look this morning.

Injuneer

Here's the list of my preferences on the export file:

Record# (inserted automatically)
TimeStamp (inserted automatically)
1 – Runtime
2 – RPM
3 – Speed
4 – TPS Volts
5 – TPS %
6 – MAP
7 – Cool Temp
8 – IA Temp
9 – Ign Volts
10 – IAC Pos
11 – AFGS (MAF cars only)
12 – Spark Advance
13 – Spark Retard
14 – Knock Count
15 – Inj BPW Left
16 – Inj BPW Right
17 – Fuel Trim Cell
18 – Left O2 mV
19 – Right O2 mV
20 – LTerm-LC
21 – LTerm-RC
22 – STerm-LC
23 – STerm-RC
24 – CCP DC
25 – EGR DC
26 – Baro
27 – IAC Pos
28 – Idle RPM
29 – Inj DC Left
30 – Inj DC Right
31 – RPM-16
32 – <OFF>

If you could export the first file, which you indicate was run actually driving the car, and not having the hesitation problem if I understand correctly.

There's not much to look at in the idle file. There is no evidence via the MAP sensor that the engine is running rough. It is surprisingly stable. If you had misfires, I'd expect to see it jumping around, just like the needle on a vacuum gauge would do.

The RPM-16 idle values also do not show up an unreasonable level of irregularities.

There has to be air getting into the system somewhere, to produce the 2 to 6 count IAC position. It wouldn't appear to be a problem with the throttle body stop screw, because the TPS closed volts are 0.63, about where most stock, unmolested systems sit.

The scan interval seems to be varying excessively, and I'm not sure how you even control that. The O2 sensor voltage, particularly the left side, seems to go high and hang there for an excessive period, but with the irregular scan time interval, it's possible we just aren't recording intermediate low voltage values. When you did the 4-wire O2 sensor conversion, did you leave wire "A" unconnected, as shown in the diagram on Rob's site?

http://shbox.com/1/heatedsensor2.jpg

Try swapping the O2 sensors side-to-side to see if the "split" reverses. That may tell you if the sensors are a problem. The right side is only an average of a 4% positive correction, so the problem appears to be on the left, where the average correction is about negative 8%.

jordankeck

The file where the car was running pretty well for alot of the time is posted at the link below, but I have to caution you that its well over 4 MB b/c it has over 18k records! I zipped the file before uploading so the file size ended up around 620 kb.

I do recall the car doing the hesitation/bogging while driving around the 15880 record mark, so that area may be worth looking at.

As I begin to better understand how the car "learn's" and adapts to the feedback from the sensors, I can now see why this log in particular is useful. The battery was unplugged for quite a while the day before while I was wiring the O2 sensors, forcing the car to forget what it had "learned" and to consequently go back to the stock programming. This is usually short lived as the car figures out that something is off from its ideal programming, hence the reason it will run rough even in open loop first thing in the morning.

I did leave Pin A unhooked when I did the 4-wire O2 swap - I actually used the Packard seals, removed the existing pin and plugged the hole in the connector. I will try swapping the O2's from side to side and see if that makes a difference.

I looked back through some of my older logs from 2012 and 2013 and it does appear that when the BLM's split that the left side is lower.

https://drive.google.com/file/d/0B7x...it?usp=sharing

Injuneer

And I'll caution that I'm going to be out of town for 3 days visiting my grand daughter. So it may be Monday before I can look at the file. Sounds like a challenge, but that's where Excel offers the ability to look for max, average and min values, add columns showing the difference between readings, etc. But it takes a while to format.

jordankeck

Got a quick update. I was looking over the vacuum harnesses to see if there were any obvious leak paths and I saw that there is a white tee located inline with the air pump line, as you see below. Through some searching I found that my 93 should not have come with this, so I picked up a vacuum cap and covered it.



I thought I would take the car for a spin to see if that made any difference, and there was some initial improvement, but the BLM spread came back. The link below is the point where the car started to run rough and the BLM spread kicked in (unfortunately I hopped in the car and took off before grabbing my laptop to log it). I did not swap the O2's yet but will be doing that tomorrow or next week (depending on time available).

https://drive.google.com/file/d/0B7x...it?usp=sharing

Injuneer

Do you have a feeling as to which of the three files you've posted is the best one to review?

Did you try swapping the O2 sensors?

jordankeck

Unfortunately I ran out of time yesterday to swap the O2's. I am hoping to do that one night this week and get a log. Should I also reset the PCM so it is not referencing the old calculated performance characteristics?

I would say that the latest log is the best to work from as that is the best representation of how the car is sitting today.

Injuneer

Doesn't matter if you reset the PCM or not. If you don't reset it, and the O2 sensor swap causes a change, you will be able to track the changes in the LTFT's as they occur. It happens pretty fast. Idle alone should produce useful info. If you do reset, it's simply a matter of comparing the new log with the most recent old log.

jordankeck

I swapped the O2's last night and then logged the car on my way into work this AM. The LTFT's still favor the left side rich and the right side lean.

https://drive.google.com/file/d/0B7x...it?usp=sharing

jordankeck

One more piece of info that may help - when I was swapping the O2's I noticed that my oil leak at the rear of the motor was still there despite replacing the rear main seal this year. I did not investigate it to see if it was the rear of the intake manifold, but could that leak be the path that air is entering the intake and throwing off the LTFT's?

I have been looking at a variety of posts and have found evidence to support this issue. Here is a link to another forum where a guy with a modded engine (mine is stock) was getting split BLM's, had an IAC count of 0 at idle, and found his intake manifold gasket to be leaking: http://www.google.com/url?sa=t&rct=j...,d.aWw&cad=rja